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Need a finishing method where cast and wrought aluminum will look the same

We have an aluminum machine made from a356T6 cast alum. and two of the parts are machined from 6061 bar. The parts are also machined but not entirely. We need a finishing process that protects/hardens and especially keeps all surfaces the same color. We have tried anodizing but the cast parts are grey and the machined bar is silver. The finished part is approx.1 cu.ft.. our first run (100 pieces.) has been bead blasted and washed and look very nice but we would like to enhance corrosion resistance and durability.

Jay Moyer
OEM Mfg. - Lancaster, Pennsylvania, USA
2003

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Have you considered Chem Film, IE: Iridite or Alodine or? That will not make it harder or improve wear resistance, but will improve corrosion resistance. Short of that, you are looking at two colors from anodize or electroless nickel or chrome plate (which both are more expensive). You might try a couple of parts with a GOOD black dye. Since the parts have been glass beaded, you may have a mottled look with the black dye.

James Watts
- Navarre, Florida
2003

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First of two simultaneous responses --

Anodizing oxidizes "aluminum" and aluminum always comes out the same color,however, 356 has more non-aluminum junk in the alloy than 6061 therefore it comes out a different color.

To get the same color AND to get corrosion protection, try zincate + alkaline electroless nickel + on top acid electroless nickel. I can name source if you e-mail me direct. However, that said, the roughness of the casting may reflect light differently from the wrought and show, as a different shade of gray.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003

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Second of two simultaneous responses --

If you have a lot of parts or volume, you might want to consider a mass finishing system before anodizing; however, you need a good sized machine.

AF Kenton
retired business owner - Hatboro, Pennsylvania
2003